The present invention relates in general to a sheet fed rotary printing machine, and in particular to a machine of the type having an auxiliary gripper system under a sheet feeding cylinder. The sheet fed rotary press of this type includes one or more sets of printing cylinders whereby the first or upstream set of cylinders cooperates with a sheet feeding table whereby the sheet from the feeding table is taken over by the auxiliary gripper which accelerates the sheet to the speed of the printing machine and transfers the sheet to the feeding cylinder.
From the DDR Pat. No. 122239 a printing machine is known in which sheets from the feeding table are taken over from below by a rocking auxiliary gripper and transferred against sheet stopping elements on the feeding table. The sheet feeding table and the sheet feeding cylinder in this known printing machine are arranged in such a manner that the plane of the feeding table intersects the circumference of the feeding cylinder. In such a mutual arrangement of the feeding table and the feeding cylinder the sheet is withdrawn from the feeding table downwardly and fed on a considerably curved circular path to the feeding cylinder. Due to the fact, however, that the front stop marks can swing back to the stop line on the feeding table only when the leading edge of the withdrawn sheet has passed the intersection point with path of movement of the front stop marks, which point is below the plane of the feeding table, the timing for the return swing of the front stop mark is disadvantageously influenced by this position of the feeding table. In other words, the operational speed or frequency and the periodic time interval for the alignment of the sheets are limited. It is particularly the shortage of alignment intervals especially in the case of high operational speeds of the printing machine which brings about the disadvantage of inadequate accuracy of the sheet alignment and consequently an impaired quality of the processed sheets.
In addition the strongly curved path of movement of the sheet to the feeding cylinder has the disadvantage that the feeding system cannot process all kinds of feed material and consequently certain kinds of the sheets can be processed only at the lower range of the rotary speeds of the machine.